Grid Shift been requested before it is used.

[aharondavid]

PROJ version: 9.3

OGRSpatialReference src;
 OGRErr error = src.importFromWkt("GEOGCS[\"WGS84 Coordinate System\",DATUM[\"WGS 1984\",SPHEROID[\"WGS 1984\",6378137,298.257223563],TOWGS84[0,0,0,0,0,0,0],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433],AUTHORITY[\"EPSG\",\"4326\"],AUTHORITY[\"SBMG\",\"LAT-LONG,LAT-LONG,WGS84,METERS\"]]");

 OGRSpatialReference dest;
 error = dest.importFromWkt("GEOGCS[\"NAD27\",DATUM[\"North_American_Datum_1927\",SPHEROID[\"Clarke 1866\",6378206.4,294.978698213898,AUTHORITY[\"EPSG\",\"7008\"]],AUTHORITY[\"EPSG\",\"6267\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AXIS[\"Latitude\",NORTH],AXIS[\"Longitude\",EAST],AUTHORITY[\"EPSG\",\"4267\"]]");

// this line make a call  to proj_network_open_cbk_type
 OGRCoordinateTransformation* ddd = OGRCreateCoordinateTransformation(&src, &dest);

two question about that code:

1. the function OGRCreateCoordinateTransformation cause a calling to proj_network_open_cbk_type which I think it to early
   because any transformation still not done yet.

2. suppose that transformation request will be only in X,Y (without Z). in this case vertical grid shift is not necessary, isn't it ?

[rouault]

Related call stack from preliminary analysis:

PROJ_DEBUG=3 PROJ_NETWORK=ON gdb --args bin/projinfo -s "GEOGCS[\"WGS84 Coordinate System\",DATUM[\"WGS 1984\",SPHEROID[\"WGS 1984\",6378137,298.257223563],TOWGS84[0,0,0,0,0,0,0],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433],AUTHORITY[\"EPSG\",\"4326\"],AUTHORITY[\"SBMG\",\"LAT-LONG,LAT-LONG,WGS84,METERS\"]]" -t "GEOGCS[\"NAD27\",DATUM[\"North_American_Datum_1927\",SPHEROID[\"Clarke 1866\",6378206.4,294.978698213898,AUTHORITY[\"EPSG\",\"7008\"]],AUTHORITY[\"EPSG\",\"6267\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AXIS[\"Latitude\",NORTH],AXIS[\"Longitude\",EAST],AUTHORITY[\"EPSG\",\"4267\"]]"

#0  0x00007ffff74f2bbf in __GI___poll (fds=0x7fffffffc3b0, nfds=2, timeout=1000) at ../sysdeps/unix/sysv/linux/poll.c:29
#1  0x00007ffff71d9c19 in ?? () from /lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#2  0x00007ffff71d3832 in ?? () from /lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#3  0x00007ffff71d3a26 in curl_multi_poll () from /lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#4  0x00007ffff71cc4b8 in curl_easy_perform () from /lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#5  0x00007ffff7d8f14c in osgeo::proj::CurlFileHandle::open (ctx=0x7ffff7fc68e0 <pj_get_default_ctx()::default_context>, url=0x5555565b3880 "https://cdn.proj.org/us_noaa_conus.tif", offset=0, 
    size_to_read=16384, buffer=0x5555565ab690, out_size_read=0x7fffffffc6b0, error_string_max_size=1024, out_error_string=0x555555eb37a0 "") at /home/even/proj/proj/src/networkfilemanager.cpp:1732
#6  0x00007ffff7d8d3fd in osgeo::proj::NetworkFile::open (ctx=0x7ffff7fc68e0 <pj_get_default_ctx()::default_context>, filename=0x5555565b3880 "https://cdn.proj.org/us_noaa_conus.tif")
    at /home/even/proj/proj/src/networkfilemanager.cpp:1300
#7  0x00007ffff7d8d8df in osgeo::proj::pj_network_file_open (ctx=0x7ffff7fc68e0 <pj_get_default_ctx()::default_context>, filename=0x5555565b3880 "https://cdn.proj.org/us_noaa_conus.tif")
    at /home/even/proj/proj/src/networkfilemanager.cpp:1326
#8  0x00007ffff7d84209 in osgeo::proj::FileManager::open (ctx=0x7ffff7fc68e0 <pj_get_default_ctx()::default_context>, filename=0x5555565b3880 "https://cdn.proj.org/us_noaa_conus.tif", 
    access=osgeo::proj::FileAccess::READ_ONLY) at /home/even/proj/proj/src/filemanager.cpp:903
#9  0x00007ffff7d873a0 in osgeo::proj::FileManager::open_resource_file (ctx=0x7ffff7fc68e0 <pj_get_default_ctx()::default_context>, name=0x5555559bb630 "us_noaa_conus.tif", 
    out_full_filename=0x555555dfa610 "", out_full_filename_size=2047) at /home/even/proj/proj/src/filemanager.cpp:1718
#10 0x00007ffff7aa71dc in osgeo::proj::io::DatabaseContext::lookForGridInfo (this=0x5555555b3960, projFilename="us_noaa_conus.tif", considerKnownGridsAsAvailable=true, 
    fullFilename='\000' <repeats 200 times>..., packageName="", url="", directDownload=@0x7fffffffcd40: false, openLicense=@0x7fffffffcd41: false, gridAvailable=@0x7fffffffcd42: false)
    at /home/even/proj/proj/src/iso19111/factory.cpp:3330
#11 0x00007ffff7a55fec in osgeo::proj::operation::SingleOperation::gridsNeeded (this=0x555555b2af20, 
    databaseContext=std::shared_ptr<class osgeo::proj::io::DatabaseContext> (use count 2, weak count 1) = {...}, considerKnownGridsAsAvailable=true)
    at /home/even/proj/proj/src/iso19111/operation/singleoperation.cpp:1642
#12 0x00007ffff7b0c1ce in osgeo::proj::operation::ConcatenatedOperation::gridsNeeded (this=0x555555eddc20, 
    databaseContext=std::shared_ptr<class osgeo::proj::io::DatabaseContext> (use count 2, weak count 1) = {...}, considerKnownGridsAsAvailable=true)
    at /home/even/proj/proj/src/iso19111/operation/concatenatedoperation.cpp:937
#13 0x00007ffff7b58849 in osgeo::proj::operation::FilterResults::sort (this=0x7fffffffd050) at /home/even/proj/proj/src/iso19111/operation/coordinateoperationfactory.cpp:1393
#14 0x00007ffff7b570f4 in osgeo::proj::operation::FilterResults::andSort (this=0x7fffffffd050) at /home/even/proj/proj/src/iso19111/operation/coordinateoperationfactory.cpp:1139
#15 0x00007ffff7b0d15f in osgeo::proj::operation::filterAndSort (sourceList=std::vector of length 79, capacity 128 = {...}, context=..., 
    extent1=std::shared_ptr<class osgeo::proj::metadata::Extent> (empty) = {...}, extent2=std::shared_ptr<class osgeo::proj::metadata::Extent> (use count 3, weak count 1) = {...})
    at /home/even/proj/proj/src/iso19111/operation/coordinateoperationfactory.cpp:1651
#16 0x00007ffff7b361c7 in osgeo::proj::operation::CoordinateOperationFactory::createOperations (this=0x5555569dad70, sourceCRS=..., targetCRS=..., context=...)
    at /home/even/proj/proj/src/iso19111/operation/coordinateoperationfactory.cpp:7018
#17 0x000055555557946f in <lambda()>::operator()(void) const (__closure=0x7fffffffd470) at /home/even/proj/proj/src/apps/projinfo.cpp:953
#18 0x000055555557a181 in outputOperations (dbContext=std::shared_ptr<class osgeo::proj::io::DatabaseContext> (use count 2, weak count 1) = {...}, 
    sourceCRSStr="GEOGCS[\"WGS84 Coordinate System\",DATUM[\"WGS 1984\",SPHEROID[\"WGS 1984\",6378137,298.257223563],TOWGS84[0,0,0,0,0,0,0],AUTHORITY[\"EPSG\",\"6326\"]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433],AU"..., sourceEpoch="", 
    targetCRSStr="GEOGCS[\"NAD27\",DATUM[\"North_American_Datum_1927\",SPHEROID[\"Clarke 1866\",6378206.4,294.978698213898,AUTHORITY[\"EPSG\",\"7008\"]],AUTHORITY[\"EPSG\",\"6267\"]],PRIMEM[\"Greenwich\",0,AUTHORITY[\"EPSG\",\"8901\"]],UN"..., targetEpoch="", bboxFilter=std::shared_ptr<class osgeo::proj::metadata::Extent> (empty) = {...}, 
    spatialCriterion=osgeo::proj::operation::CoordinateOperationContext::SpatialCriterion::STRICT_CONTAINMENT, spatialCriterionExplicitlySpecified=false, 
    crsExtentUse=osgeo::proj::operation::CoordinateOperationContext::SourceTargetCRSExtentUse::SMALLEST, 
    gridAvailabilityUse=osgeo::proj::operation::CoordinateOperationContext::GridAvailabilityUse::KNOWN_AVAILABLE, 
    allowUseIntermediateCRS=osgeo::proj::operation::CoordinateOperationContext::IntermediateCRSUse::IF_NO_DIRECT_TRANSFORMATION, pivots=std::vector of length 0, capacity 0, authority="", 
    usePROJGridAlternatives=true, showSuperseded=false, promoteTo3D=false, normalizeAxisOrder=false, minimumAccuracy=-1, outputOpt=..., summary=false) at /home/even/proj/proj/src/apps/projinfo.cpp:976
#19 0x000055555557ea23 in main (argc=5, argv=0x7fffffffdbf8) at /home/even/proj/proj/src/apps/projinfo.cpp:1701

We might need to convince DatabaseContext::lookForGridInfo() or its callers in the above call context to not call NS_PROJ::FileManager::open_resource_file() (in PROJ_NETWORK / PROJ_GRID_AVAILABILITY_KNOWN_AVAILABLE mode)